CVE-2017-6021 in ClearSCADA
Summary
by MITRE
In Schneider Electric ClearSCADA 2014 R1 (build 75.5210) and prior, 2014 R1.1 (build 75.5387) and prior, 2015 R1 (build 76.5648) and prior, and 2015 R2 (build 77.5882) and prior, an attacker with network access to the ClearSCADA server can send specially crafted sequences of commands and data packets to the ClearSCADA server that can cause the ClearSCADA server process and ClearSCADA communications driver processes to terminate. A CVSS v3 base score of 7.5 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 02/04/2020
The vulnerability identified as CVE-2017-6021 represents a critical denial of service flaw affecting Schneider Electric ClearSCADA versions through 2015 R2, with a CVSS score of 7.5 indicating high severity. This vulnerability resides within the ClearSCADA server process and communications driver components, specifically targeting the server's handling of incoming command sequences and data packets. The flaw allows unauthenticated attackers with network access to the ClearSCADA server to craft and transmit malicious packet sequences that trigger process termination, effectively disrupting industrial control system operations. The vulnerability impacts multiple product versions including ClearSCADA 2014 R1 through R1.1, 2015 R1, and 2015 R2, suggesting a widespread exposure across the product line. This issue falls under CWE-400, which categorizes it as an uncontrolled resource consumption vulnerability, specifically manifesting as a resource leak or process termination through malformed input. The attack vector requires only network access to the target system, making it particularly dangerous in industrial environments where such systems are often directly connected to operational networks.
The technical exploitation of this vulnerability occurs through the manipulation of command sequences sent to the ClearSCADA server, where specific combinations of data packets can cause the server process and associated communications drivers to crash or terminate unexpectedly. This type of attack directly violates the availability principle of the CIA triad, as it prevents legitimate users from accessing critical industrial control system functions. The vulnerability's impact extends beyond simple service interruption, as ClearSCADA servers typically manage critical infrastructure operations including process control, data acquisition, and supervisory control functions. When these servers terminate unexpectedly, they can cause cascading failures throughout the industrial control network, potentially leading to operational disruptions, safety hazards, or even physical damage to equipment. The lack of authentication requirements for exploitation means that any network-connected attacker can potentially trigger this vulnerability, making it particularly concerning for industrial environments where network boundaries may not be properly secured.
The operational impact of CVE-2017-6021 is severe within industrial control system environments, as ClearSCADA servers serve as central points of control for critical infrastructure operations. When these servers crash or terminate, they can cause immediate disruption to process control, data logging, and supervisory functions, potentially leading to loss of operational visibility and control. The vulnerability's potential for remote exploitation without authentication means that attackers can cause service disruption from outside the facility's network perimeter, especially in environments where industrial control systems are not properly isolated. This vulnerability directly aligns with ATT&CK technique T1499.001, which covers network disruption through resource exhaustion or process termination, and can be classified under the broader category of industrial control system attacks. The risk is amplified in environments where ClearSCADA systems control critical manufacturing processes, power generation, or water treatment facilities, where even brief service interruptions can result in significant financial losses or safety incidents.
Organizations affected by CVE-2017-6021 should implement immediate mitigations including network segmentation to isolate ClearSCADA servers from general network access, applying available vendor patches when released, and implementing network monitoring to detect anomalous packet sequences. The vulnerability's classification as a resource consumption issue under CWE-400 suggests that input validation and robust error handling should be enhanced in the affected ClearSCADA components. Security teams should also consider implementing intrusion detection systems specifically configured to monitor for the packet patterns that could trigger this vulnerability, as well as establishing incident response procedures for rapid recovery from service interruption events. Additionally, organizations should conduct comprehensive assessments of their industrial control system environments to identify all instances of affected ClearSCADA versions and ensure proper network access controls are implemented to prevent unauthorized access to these critical systems. The vulnerability demonstrates the importance of maintaining up-to-date security patches in industrial control environments, where the consequences of service disruption can be far more severe than typical enterprise network attacks.